I’ve met plenty of Russians. Educated ones are generally capable of producing very good English especially if the subject is technical. Outside the Anglosphere speaking another foreign language well is not uncommon.

Options:

Someone being very bad at pretending to be Russian.

Russians pretending to be very bad at pretending to be Russian because Russians find that hilarious. Fake Russians in movies (Red Heat is a particular favorite) are so funny in a so bad it is good way that the genre and phenomenon, I’m told, has its own name: клюква. (cranberry)